[Feature]: Allow for the blocklist client to be unset

[djordon]

Feature - Allow for the blocklist client to be unset

1. Description

We don't need a blocklist client, and someone can choose to run their signer without one. In this case, the signer should still run correctly and we should skip the code path that does blocklist checks.

1.1 Context & Purpose

2. Technical Details:

Make the blocklist config optional and have the SignerContext object optionally return a blocklist client. When there isn't a config for the blocklist client, have an warn log and have all can_accept calls to the blocklist client return Ok(true) (or whatever would be equivalent).

2.1 Acceptance Criteria:

• Allow for the blocklist client to be unset in the config.

3. Related Issues and Pull Requests (optional):